In order to determine whether or not the price of a book can be determined by th
ID: 3155912 • Letter: I
Question
In order to determine whether or not the price of a book can be determined by the number of pages it contains, a college professor recorded the number of pages and price for 15 books on one shelf. The data are shown below.
*Denotes Hardback Book
a. Relating # of pages and price, would you expect a positive or negative correlation?
b. Construct scatterplot and calculate Pearson correlation coefficient. Depict type of book on your scatterplot.
c. Construct scatterplot and calculate Pearson correlation coefficient using just the data for the hardback books.
d. Construct scatterplot and calculate Pearson correlation coefficient using just the data for the paperback books.
e. What do you learn from parts b, c, and d above.
Pages
Price
Pages
Price
Pages
Price
104*
32.95
342*
49.95
436
5.95
188*
24.95
378
4.95
458*
60.00
220*
49.95
385
5.99
466*
49.95
264*
79.95
417
4.95
469
5.99
336
4.50
417*
39.75
585
5.95
Pages
Price
Pages
Price
Pages
Price
104*
32.95
342*
49.95
436
5.95
188*
24.95
378
4.95
458*
60.00
220*
49.95
385
5.99
466*
49.95
264*
79.95
417
4.95
469
5.99
336
4.50
417*
39.75
585
5.95
Explanation / Answer
a. We expect that as number of pages increases price increases. Hence there would be positive correlation.
b) The scatter plot is given by,
Correlation coefficient is :
Excel command : '=correl(range of x's, range of y's ) '
So r = -0.3121
c) Scatter plot for hardback book
Pearson correlation coefficient = r = 0.35
d. Scatter plot of paperback books
pearson correlation coefficient = r = 0.64
e) From part b we say that , the overall correlation between price and pages is negative where we expect it as positive. But from c and d wee say that the correlation between pages and hardback books is positive but it is not strong positive correlation. But the correlation between paperback books and pages is strong positive.
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